docs: def getFactors(self, aLocation, axisOnly=False, allFactors=False):
          """
              Return a list of all factors and math items at aLocation.
              factor, mathItem, deltaName
              all = True: include factors that are zero or near-zero
          """
          deltas = []
          aLocation.expand(self.getAxisNames())
          limits = getLimits(self._allLocations(), aLocation)
          for deltaLocationTuple, (mathItem, deltaName) in sorted(self.items()):
              deltaLocation = Location(deltaLocationTuple)
              deltaLocation.expand( self.getAxisNames())
              factor = self._accumulateFactors(aLocation, deltaLocation, limits, axisOnly)
              if not (factor-_EPSILON < 0 < factor+_EPSILON) or allFactors:
                  # only add non-zero deltas.
                  deltas.append((factor, mathItem, deltaName))
          deltas = sorted(deltas, key=itemgetter(0), reverse=True)
          return deltas